Recent developments in zeolite catalysis and hydrocarbon conversion processes have created interest in utilizing olefinic feedstocks, for producing C.sub.5.sup.+ gasoline, diesel fuel, etc. In addition to the basic work derived from ZSM-5 type zeolite catalysts, a number of discoveries have contributed to the development of a new industrial process, known as Mobil Olefins to Gasoline/Distillate ("MOGD"). This process has significance as a safe, environmentally acceptable technique for utilizing feedstocks that contain lower olefins, especially C.sub.2 -C.sub.5 alkenes. In U.S. Pat. Nos. 3,960,978 4,021,502, Plank, Rosinski and Givens disclose conversion of C.sub.2 -C.sub.5 olefins, alone or in admixture with paraffinic components, into higher hydrocarbons over crystalline zeolites having controlled acidity. Garwood et al have also contributed improved processing techniques to the MOGD system, as in U.S. Pat. Nos. 4,150,062, 4,211,640 and 4,227,992. The above-identified disclosures are incorporated herein by reference.
Conversion of lower olefins, especially propene and butenes, over HZSM-5 is effective at moderately elevated temperatures and pressures. The conversion products are sought as liquid fuels, especially the C.sub.5.sup.+ aliphatic and aromatic hydrocarbons. Olefinic gasoline can be produced in good yield by the MOGD process and may be recovered as a product or fed to a low severity reactor system for further conversion to distillate-range products. Distillate mode operation can be employed to maximize production of C.sub.10.sup.+ aliphatics by reacting the lower olefins at high pressure and moderate temperature. Operating details for typical MOGD units are disclosed in U.S. Pat. Nos. 4,456,779; 4,497,968 (Owen et al) and No. 4,433,185 (Tabak), incorporated herein by reference.
In the process for catalytic conversion of olefins to heavier hydrocarbons by catalytic oligomerization using an acid crystalline zeolite, such as ZSM-5 type catalyst, process conditions can be varied to favor the formation of either gasoline or distillate range products. At moderate temperature and relatively high pressure, the conversion conditions favor distillate range product having a normal boiling point of at least 165.degree. C. (330.degree. F.). Lower olefinic feedstocks containing C.sub.2 -C.sub.6 alkenes may be converted selectively; however, the low severity distillate mode conditions do not convert a major fraction of ethene. While propene, butene-1 and others may be converted to the extent of 50 to 95% in the distillate mode, only about 10 to 30% of the ethylene component will be converted.